Electronic switches



June 16, 1959 LERBS 2,891,150

ELECTRONIC SWITCHES Filed A il 14, 1954 4 Sheets-Sheet 1 June 16', 1959 LERBS V Q 2,891,150

ELECTRONIC SWITCHES 4 Sheets-Sheet 5 A. LERBS ELECTRONIC SWITCHES FIG. 6

FIG. 8

June 16, 1959 Filed April 14, 1954 Julie 16, 1959 LERBS 189L150 ELECTRONIC SWITCHES Filed April 14, 1954 4 Sheets-Sheet 4 United States Patent Ofitice Patented June 16, 1959 ELECTRONIC SWITCHES Alfred Lerbs, Paris, France, assignor to Compagnie Generale de Telegraphic Sans Fil, a corporation of France Application April 14, 1954, Serial No. 423,204

Claims priority, application France April 16, 1953 19 Claims. (Cl. 250-27) Electronic switches of known type generally use either vacuum tubes or thyratrons. Each of these two types has its advantages and disadvantages. Vacuum tubes allow the passage of pulses of accurately rectangular shape and at intervals of time which may be short. However, the power required for grid control may be considerable. Thyratrons on the other handrequire only low power but the pulses obtained are less perfectly rectangular and the frequency of pulserepetition is limited.

The present invention has for its object to provide an electronic switch for direct current circuits which com bines the advantages of vacuum tubes with those of thyratrons Without possessing their disadvantages.

The direct current switch according to the invention comprises a vacuum tube including an anode and a oathode between which is connected the switch controlling source and at least one other electrode which is positively biased relative to the cathode, the circuit to be controlled being connected between the cathode and this third electrode. Inside the tube prevails a magnetic field which prevents the electrons emitted by the-cathode from attaining the anode and deflects them in the direction of the third electrode.

The invention will be better understood with the aid of the ensuing description with reference to the accompanying drawing in which,

Fig. l is a diagrammatic view in cross section of a first embodiment of the switch according to the invention;

Fig. 2 is a similar diagrammatic view of a pulse-controlled switch according to the invention;

Figs. 3 and 4 show two modifications of the switch shown in Fig. 1;

;Figs. 5 to 8 are diagrammatic views, the first in crosssection and the others in aXial section,.of some other modifications of the switch according to the invention;

Fig. 9 is a more. detailedview in axial section of a switch of the type shown in Fig. 6.

Referring now to Fig. l the. switch according to the invention comprises a cylindrical electrode 1 which defines an envelope surrounding a second electrode in the form of a cylinder 3. The latter includes a slot or groove 3a in which is disposed a cathode 2. The two electrodes 1 and 3am insulated from one another and the tube thus formed is evacuated. The surface of the cylinder 3 has a coefficient of secondary emission which is as low as possible and in any case less than one; For the sake of clarity the heating filament of the cathodehas not been shown. A magnetic field perpendicular to the plane of the drawing is generated inside the tube by any appropriate means. Its amplitude should be such that the electrons emitted by the cathode 2 do not attain the anode 1. The switch is inserted by meansof its terminals A and lit in series in the circuit 4 to be controlled this circuit being fed by a source 6, the terminals A andB being connected to the'electrodes 2 and 3 respectively. The electrode} is therefore biased by' this source 6.

A source of control voltage '5is connected between the Z cathode 2 and the anode 1. This source may be a direct, alternating or pulsating voltage.

The switch shown in Fig. 1 operates in the following manner:

It will be supposed that the current emitted by the cathode 2 is limited only by the space charge. As soon as the control voltage is applied from the source 5, the electrons follow, as is known, cycloidal paths about the central electrode 3 and then settle on the surfiace of the latter at a velocity which is low compared to the velocity imparted to the electrons by the anode voltage. The circuit 4 is thus closed by the switch.

In order to be able to use the switch for cutting off higher currents than the current capable of being emitted by the cathode, according to another feature of the invention there is disposed along the path followed by the electrons emitted by the cathode an electrode having a high secondary emission factor, in any case with an emission factor higher than one.

Such a switch is shown in Fig. 2 where a secondary emission electrode 7 is connected directly to the cathode 2. A part of the electrons emitted by the cathode fall on the electrode 7 and this gives rise to a secondary emission. Electrode 7 together with electrode 3 forms a system of revolution, which is coaxially surrounded by anode 1.

In the embodiment shown in Fig. 2, the switch controlling source delivers an alternating, and preferably pulsating, voltage.

The supply source 6 of the controlled circuit 4 is connected to the two terminals A and B of the switch and is shunted by a capacitor 8. A choke coil 9 is inserted in series with this source. The circuit 4 to be controlled is inductively coupled to the circuit between A and B through a transformer 16. A cathode heating source, has been diagramamtically shown at D.

Fig. 3 shows a switch. of similar type to that shown in Fig. l but in which the anode 1 is located inside the cylinder and the negative electrodes 2, 3 and 7 outside the latter. This arrangement may be advantageous when it is desired to ground the cathode 2. When the switch is pulse controlled, it may be advantageous to use an auxiliary control anode 10. Such a switch is shown in Fig. 4. Pulses are applied in this instance through a transformer 15. Electrode 10 is biased by the source 6 to a level equal to the highest level of control pulses. For the remaining parts, the switch shown in Fig. 4 is similar to that shown in Fig. 2. The use of the electrode 10 decreases the capacitance between the two electrodes 1 and 7, between which the control signal is applied. This is important particularly if the switch is pulse controlled by means of rectangular pulses the 2, 3 and 7 is not necessarily constant.

to build up an electron optical system for improving the form of the electron paths in such manner as to increase the angle incidence, thereby intensifying the secondary emission. i a

To the same-end, thecathode maybe biased with a source ofnegative potential with respect to the secondary emission electro de.

In th'e embodiments diagrammatically shown in axial section in Figs. 6 to 9, the electrode 3 may be given the form of a disc placed between two parallel emitting .electrodes 7' and 7", which are also in the. form of.discs Each of these discs carries a cathode 2. In order to ensure that the electrons emitted by the cathodes 2 reach the electrode 3, it is necessary to create in the electric field a small component which is directed towards the plane of symmetry of the system (arrows 12 in Fig. 6). This component may be readily created by giving to the electrodes 7' and 7" the form of truncated cones which converge in the direction of the plane of symmetry. For purposes of slowing down the electrons when they are in the proximity of the electrode 3, an electric field component of opposite direction (arrows 13 in Fig. 7) may be created. This component may be obtained for example by providing the electrode 3 with a circular rib 17 which is positioned in front of a circular groove 18 provided in the electrode 1, so that the electric field in front of the electrode 3 is weakened, in a manner similar to that of the solution consisting in progressively increasing the distance between the electrode 1 and the electrode 3 in the tube shown in Fig. 5.

In the switch shown in Fig. 8, the electrodes 3, 7 and 7 have the form of discs or truncated cones which are truncated slantwise to the axis of the system. The tube incorporates features to be found in those shown in Figs. 1 to and in those shown in Figs. 6 and 7. The electrons issuing from the cathodes 2 attain the electrode 3 both by being propagated along the axis of the system as is the case of the tube shown in Figs. 6 and 7, and by being propagated in planes perpendicular to the axis .of the system as is the case in the tube shown in Figs. 1 to 5.

Fig. 9 shows in more detail a switch according to the invention. The electrodes 7' and 7", each supporting a cathode 2, are secured to the inwardly facing end walls of a cylindrical casing 19 which is grounded. The anode 1 is annular and is supported inside the casing 19 by insulating elements 20. The electrode 3 is supported inside the casing 19 by insulating elements 21 of, for .example, quartz inserted in the electrodes 7. A magnet 14 provides the magnetic field necessary according to the invention. It comprises an opening 22. through which extend the cathode heating conductors diagrammatically shown at 23 and the conductor, in the form of a rod 24', to the electrode 3. The two terminals A and B of the switch are also to be seen in this figure.

Such a tube is of a very simple and rugged design.

The switch according to the invention has many applications, particularly in the field of radar, high-power pulse modulators, high voltage line switching, etc.

What I claim is:

.1. in a circuit connected to a direct current source having a positive and a negative terminal, an electronic switch constituted by a high vacuum electron tube com prising: a non electron permeable anode; a cathode for emitting an electron beam; means for applying a control voltage between said anode and cathode; a third electrode electrically insulated from said cathode; fourth electrode means having a high secondary emission ratio, and elec trical-ly connected to said cathode and insulated from said third electrode; means for providing a magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufficient strength for.

deflecting said beam toward said third and fourth electrodes; a first terminal connected to said cathode for connection to said negative direct current terminal; and a second terminal connected to said third electrode for con nection to said positive direct current terminal.

2. A circuit according to claim 1 wherein said anode is of circular shape and surrounds said third and said fourth electrodes which are parts of a cylinder coaxial with said anode and constituted by said third and fourth electrodes separated by an interval, said fourth electrode being provided with a groove where .said cathode is cated.

--3. A circuit according to claim 1, wherein said :fourth electrode is of circular shape and surrounds said, anode 4 I which is in the shape of a cylinder coaxial with said fourth electrode.

4. A circuit according to claim 1, wherein said fourth electrode is provided with a groove where said cathode is located and surrounds said anode which is in the shape of a cylinder coaxial with said fourth electrode, said third electrode being in the shape of a cylindrical segment located in a recess provided in the internal wall of said fourth electrode.

'5. In a circuit connected to a direct current source .having a positive and a negative terminal, an electronic switch constituted by a high vacuum electron tube comprising: an anode; a cathode for emitting an electron beam; means for applying a control pulse voltage between said anode and cathode; a third electrode electri cally insulated from said cathode; fourth electrode means, having a high secondary emission ratio, and electrically connected to said cathode and insulated from said third electrode; means for providing a magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufiicient strength for deflecting said beam from said anode and toward said third and fourth electrodes; a first terminal connected to said cathode -for connection to said negative direct current terminal; and a second terminal connected to said third electrode for connection to said positive direct current terminal; a transformer having a primary winding and a secondary winding, said primary winding being series connected between said second terminal and said positive di-. rect current terminal and, said secondary winding being connected across the circuit to be controlled.

6. In a circuit connected to a direct current source having a positive and a negative terminal, an electronic switch constituted by a high-vacuum electron tube comprising: an anode; a cathode for emitting an electron beam; means for applying a control voltage between said anode and cathode; a third electrode electrically insulated from said cathode; a fourth electrode having a high secondary emission ratio, electrically connected to said cathode and insulated from said third electrode; a fifth electrode electrically insulated from the other electrodes; means for biassing said fifth electrode with direct current to a level equal to the highest level of said control voltage; means for providing a magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field, provided by said control voltage and being of sufiicient strength, for deflecting said beam toward said third electrode; a first terminal connected .to said cathode for connection to said negative direct current terminal; and a second terminal connected to said third electrode for connection to said positive direct current terminal.

7. In a circuit connected to a direct current source having a positive and a negative terminal, an electronic switch constituted by a high vacuum electron tube com-. prising: an anode; a cathode for emitting an electron beam; means for applying a control voltage between said anode and cathode; a third electrode electrically insulated from said cathode; a fourth electrode electrically insulated from the other electrodes; means for biassing said fourth electrode with direct current to a level equal to the highest level of said control voltage; means for providing a magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufficient strength for deflecting said beam from said anode; a first terminal connected to said cathode for connection to said negative direct current terminal and a second terminal connected to said third electrode for connection to said positive direct current terminal.

8. A switch according to claim 7 wherein said anode is in the shape of a cylindrical segment located in arecess of a wall of said fourth electrode, whereby said anode and fourth electrode define a substantially continuous cylindrical wall surrounding said cathode and third electrode. t t

9. In a circuit connected to a direct current source having a positive and a negative terminal, an electronic switch constituted by a high vacuum electron tube comprising an anode; a cathode for emitting an electron beam; means for applying a control pulse voltage between said anode and cathode; a third electrode electrically insulated from said cathode; a fourth electrode electrically insulated from the other electrodes; means for providing a magnetic minal and said positive direct current terminal, said secondary being connected across a circuit to be controlled; and said fourth electrode being further connected to said positive direct current terminal.

10. A circuit comprising a direct current source having a positive and a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising: a non electron permeable anode of annular shape; within said anode a first, a second and a third disk shaped electrodes coaxial with said anode, located side by side and in spaced relationship; the surfaces of said first and third electrodes having a high secondary emission ratio; two electron beam emissive cathodes respectively located in external grooves in said first and third electrodes; means forapplying a control voltage between said anode and cathodes, thereby establishing an electric field therebetween; means for providing an electric field component in a direction perpendicular to the symmetry plane of the system around said first and third electrodes; means for providing a magnetic field having its lines of force parallel to the axis of said disk shaped electrodes and being of suflicient strength for preventing said beams from reaching said anode and tor deflecting them toward said electrodes; a first terminal connected to said cathodesand to said negative direct current terminal and a second terminal connected to said second electrode and to said positive direct current terminal.

11. A circuit comprising a direct current source having a positive and a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising: a non electron permeable anode of annular shape; Within said anode, a first, a second and a third disk shaped electrodes coaxial with said anode, located side by side and in spaced relationship; said first and third electrode being in the shape of truncated cones, said second electrode being of cylindrical shape; the surfaces of said first and third electrodes having a high secondary emission ratio; two electron beam emissive cathodes respectively located in external grooves in said first and third electrodes; means for providing a magnetic field having its lines of force parallel to the axis of said disk shaped electrodes and being of sufficient strength for preventing said beams from reaching said anode and for deflecting them toward said electrodes; a first terminal connected to said cathodes and to said negative direct current terminal and a second terminal connected to said second electrode and to said positive direct current terminal; and means for applying a control voltage between said anode and cathodes.

12. A circuit comprising a direct current source having a positive and a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising: a non electron permeable anode of annular shape; Within said anode a first, a second and a third disk shaped electrodes coaxial with said anode, located side by side and in spaced relationship; said first and thir'd electrodes being in the shape of truncated cones whose tops are bevelled in opposite directions, the adjacent sides of said second electrode being respectively parallel thereto;,the surfaces of said first and third electrodes having a high secondary emission ratio; two electron beam emissive cathodes respectively located in external grooves in said first and third electrodes; means for providing a magnetic field having its lines of force parallel to the axis of said disk shaped electrodes and being of sufiicient strength for preventing said beams from reaching said anode and for deflecting them toward said electrodes; a first terminal connected to said cathodes and to said negative direct current terminal and a second terminal connected to said second electrode and to said positive direct current terminal; and means for applying a control voltage between said anode and cathodes.

13. A circuit comprising a direct current source having a positive and a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising: a non electron permeable anode of annular shape; within said anode a first, a second and a third disk shaped electrodes coaxial with said anode, located side by side and in spaced relationship; said second electrode having a central peripheral projection directed towards said anode and said anode having an internal groove located opposite said projection; the surfaces of said first and third electrodes having a high secondary emission ratio; two electron beam emissive cathodes respectively located in external grooves in said first and third elec trodes; means for providing a magnetic field having its lines of force parallel to the axis of said disk shaped electrodes and being of suflicient strength for preventing said beams from reaching said anode and for deflecting them toward said electrodes; a first terminal connected to said cathodes and to said negative direct current terminal and a second terminal connected to said second electrode and to said positive direct current terminal; and means for applying a control voltage between said anode and cathodes.

14. A circuit according to claim 1 wherein said anode and said third and fourth electrodes constitute respective coaxial systems of revolution, the distance between said systems varying along their opposed peripheries.

15. In a circuit connected to a direct: currentsource.

switch constituted by a high vacuum electron tube comprising: a non-electron permeable cathode for emitting an electron beam; non electron permeable anode shaped at least in part as a hollow cylinder; a cylindrical third electrode surrounded by said anode and provided with a groove, said cathode being located in said groove and electrically insulated from said third electrode; means for applying a control voltage between said anode and cathode; means for establishing through said beam a switchable connection between said cathode and anode adapted to be switched on and off thereby including means for providing a magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufiicient strength for substantially preventing said beam from reaching said anode and for deflecting said beam toward said third electrode; a first terminal connected to said cathode and to said negative direct current terminal; and a second terminal connected to said third electrode and to said positive direct current terminal.

16. In a circuit connected to a direct current source having a positive and a negative terminal, an electronic switch constituted by a high vacuum electron tube comprising: a non electron permeable cathode for emitting a non electron permeable electron beam; an anode shaped at least in part as a hollow cylinder; a cylindrical third electrode surrounded by said anode and provided with a groove, said cathode being located in said groove and electrically insulated from said third electrode; means for applying a control pulse voltage between said anode and cathode; means for establishing through said beam a switchable Connection between said cathode and anode adapted to be switched on and off thereby including means for providinga magnetic field having its lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sutficient strength for substantially preventing said beam fromreaching said anode and for deflecting said beam toward said third electrode; a first terminal connected to said cathode and to said negative direct current terminals; a second terminal connected to said third electrode and to said positive direct current terminal; and a'transformer having a primary winding and a secondary winding, said primary winding being series connected between said second terminal and said positive direct terminal, and said secondary winding being connected across a circuit to becontrolled.

17. A circuit comprising a direct current source having a positive and a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising:- an anode; a cathode for emitting an electron beam; a third electrode electrically insulated from said cathode; means for establishing through said beam a switchable connection between said cathode and said third electrode adapted to be switched on and off thereby including means for applying a controlvoltage between said anode and cathode; and means providing a magnetic field having its lines of force essential-1y perpendicular to said beam and to the lines of force of theelectric field provided bysaid control voltage and being of sufii cient strength for substantially preventing said beam from reaching said anode and for deflecting said beam toward said third. electrode; a first terminal connected to said cathode and to said negative direct current terminal; and a second terminal connected to said third electrode and to said positive direct current terminal.

18. A circuit comprising a direct current source having a positiveand a negative terminal, and an electronic switch constituted by a high vacuum electron tube comprising: an anode, a cathode for emitting an electron beam; a third electrode electrically insulated from said cluding means for applying a control pulse voltage be- (lit tween said anode. and cathode, and means for providinga magnetic field having its lines of force essentially penv pendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufiicient strength for deflecting said beam from said anode; a first terminal connected to. said cathode and to said negative direct current terminal; and a. second terminalconnected to said third electrode and to said positive direct current terminal; and a transformer having a primary Winding and a secondary winding, said. primary winding being series connected between said second terminal and said positive direct current terminal and said secondary winding being connected acrossfa circuit to be controlled. 19. A circuit comprising a high vacuum electron tub including an anode, a cathode for emitting an electron beam and a third electrodeelectrically insulated from.

said cathode; means for establishing through said beam a switchable connection between said cathode and saidthird electrode adapted to be switched on and ofi therebyincluding means for applying a control voltage between said anode and cathode, and means for'providing a magnetic field havingits lines of force perpendicular to said beam and to the lines of force of the electric field provided by said control voltage and being of sufiicient strength for substantially preventing said beam from reaching said anode and for deflecting said beam toward said third electrode; adirect current source having its negative terminalconnected to said cathode and its.posi-' ti-ve terminal connected to said third electrode; and means for switching on-and-oii said control voltage thereby to switch on and off said direct current source.

References Cited in the file of this patent UNITED STATES PATENTS Aasma et al. July 9, 1957 

